JPH06325765A - Nonaqueous electrolytic secondary battery and its manufacture - Google Patents

Abstract

PURPOSE:To provide a new nonaqueous electrolytic secondary battery and its manufacture where the battery is of high voltage and high energy density, excellent in charge/ discharge characteristics, concurrently durable in cyclic life, and is high in reliability. CONSTITUTION:In a nonaqueous electrolytic secondary battery composed of a negative electrode, a positive electrode, and at least, of lithium ion conductive nonaqueous electrolyte, silicon oxide containing lithium or cilicic acid salt is used as negative electrode active material. The lower silicon oxide is particularly used, which is represented by a composition formula LixSiOy (where, x<=0, and 2>y>0), and contains lithium. By this constitution, the secondary battery can thereby be obtained, in which negative electrode active material is low in potential, and is a base metal, charge/ discharge capacity is high in the potential area of low voltage of 0 to 1V in respect to litium, moreover, voltage is high, and energy density is also high because polarization (internal resistance) is low at the time of charge/discharge. And furthermore, the battery is excellent in high amperage current charge/discharge characteristics, concurrently is less deteriorated by over charging/over discharging, is durable in cyclic life, and is high in reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery using a lithium ion conductive non-aqueous electrolyte as a negative electrode active material, which is capable of inserting and extracting lithium, and particularly to a high voltage, The present invention relates to a novel negative electrode active material that provides a novel secondary battery having high energy density, excellent charge / discharge characteristics, long cycle life, and high reliability, and an electrolyte and a positive electrode active material suitable for the novel negative electrode active material.

[0002]

Non-aqueous electrolyte batteries using lithium as a negative electrode active material have advantages of high voltage, high energy density, small self-discharge and excellent long-term reliability. It has already been widely used as a power source for industrial use. However, with the remarkable development of portable electronic devices and communication devices in recent years,
A wide variety of devices that require a large current output for batteries as power sources have appeared, and rechargeable / dischargeable secondary batteries with high energy density have been strongly demanded from the viewpoint of economy and reduction in size and weight of devices. ing. Therefore, research and development for promoting the non-aqueous electrolyte battery having a high energy density into a secondary battery have been actively carried out and partially put into practical use, but energy density, charge / discharge cycle life, reliability, etc. are still unsatisfactory. It is enough.

Conventionally, as the positive electrode active material constituting the positive electrode of this type of secondary battery, depending on the form of charge / discharge reaction, the following 3
Some types of species have been found. The first type is a metal chalcogenide such as TiS ₂ , MoS ₂ , NbSe ₃ or MnO ₂ , MoO ₃ , V ₂ O ₅ , Li _X Co.
_{O 2, Li X NiO 2,} Li x Mn 2 O 4 or the like as a so metal oxides, crystalline interlayer and lattice positions or interstitial gap lithium-ion (cation) only intercalation, deintercalation Type that goes in and out depending on the reaction. The second type is polyaniline, polypyrrole,
A type in which mainly anions are stably doped and de-doped due to conducting reactions such as conductive polymers such as polyparaphenylene. The third type is a type (intercalation, deintercalation or dope, in which both lithium cations and anions can enter and exit, such as graphite intercalation compounds and conductive polymers such as polyacene.
Dedoping etc.).

On the other hand, as the negative electrode active material constituting the negative electrode of this type of battery, when metal lithium is used alone, the electrode potential is the most base, so that the positive electrode using the positive electrode active material as described above is used. The combined battery has the highest output voltage and high energy density, which is preferable, but there was a problem that dendrites and passivation compounds were formed on the negative electrode during charging and discharging, and deterioration due to charging and discharging was large and cycle life was short. . In order to solve this problem, as a negative electrode active material, (1) lithium and Al, Zn, Sn, Pb, Bi, Cd
Alloys with other metals such as (2) WO ₂ , MoO ₂ , Fe ₂
An intercalation compound or an intercalation compound in which lithium ions are occluded in the crystal structure of an inorganic compound such as O ₃ or TiS ₂ , graphite, or a carbonaceous material obtained by firing an organic substance, (3) lithium ion-doped polyacene, It has been proposed to use a substance capable of inserting and extracting lithium ions, such as a conductive polymer such as polyacetylene.

[0005]

However, generally, a negative electrode using a material capable of inserting and extracting lithium ions other than metallic lithium as described above as a negative electrode active material, and a positive electrode active material as described above are used. When a battery is constructed by combining the positive electrode and the negative electrode active material, the electrode potential of these negative electrode active materials is nobler than the electrode potential of metallic lithium. It has the drawback of being significantly lower. For example, lithium and A
0.2 to 0.8 V when using an alloy such as 1, Zn, Pb, Sn, Bi, Cd, 0 to 1 V for a carbon-lithium intercalation compound, and 0 for a lithium ion insertion compound such as MoO ₂ or WO _2. The operating voltage is reduced by 0.5 to 1.5V.

Further, since elements other than lithium also serve as negative electrode constituents, the capacity and energy density per volume and weight are significantly reduced. Furthermore, when the alloy of (1) above with lithium and another metal is used, the utilization efficiency of lithium during charging and discharging is low, and cracks occur in the electrode due to repeated charging and discharging, and the like. Therefore, there is a problem that the cycle life is short, and in the case of the lithium intercalation compound or the intercalation compound of (2), there is deterioration such as collapse of the crystal structure or generation of an irreversible substance due to overcharge and discharge, and a high electrode potential ( Since there are many (noble) batteries, there is a drawback that the output voltage of a battery using this is low, and in the case of the conductive polymer of (3), the charge / discharge capacity, especially the charge / discharge capacity per volume is small. There's a problem.

Therefore, at high voltage and high energy density,
In addition, in order to obtain a secondary battery with excellent charge / discharge characteristics and a long cycle life, the electrode potential with respect to lithium is low (base), and the collapse of the crystal structure or the irreversible substance due to the absorption / desorption of lithium ions during charge / discharge. There is a need for a negative electrode active material that has a large amount of lithium ions that can be occluded and released reversibly without deterioration such as generation, that is, a large effective charge / discharge capacity.

On the other hand, of the above-mentioned positive electrode active materials, the first type generally has a large energy density, but has a drawback that if it is overcharged or overdischarged, it is greatly deteriorated due to crystal collapse or generation of irreversible substances. . On the contrary, the second and third types have a drawback that the charge / discharge capacity, especially the charge / discharge capacity per volume and the energy density are small.

Therefore, in order to obtain a secondary battery having excellent overcharge and overdischarge characteristics, high capacity and high energy density, there is no crystal collapse or irreversible substance formation due to overcharge and overdischarge, and A positive electrode active material having a larger amount capable of reversibly inserting and extracting lithium ions is required.

[0010]

In order to solve the above problems, the present invention provides a negative electrode active material for a battery of this type,
It is proposed to use a novel lithium ion storage / release material comprising a silicon oxide or silicate containing lithium. That is, a composite oxide of lithium and silicon containing lithium in the crystal structure or amorphous structure of silicon oxide or silicate and capable of inserting and extracting lithium ions by an electrochemical reaction in a non-aqueous electrolyte. To use. The state of lithium in this composite oxide is preferably mainly ionic, but is not necessarily limited.

The following two types of methods can be mentioned as preferable methods for producing the lithium-containing silicon oxide or silicate used as the negative electrode active material of the battery of the present invention, but the method is not limited thereto. The first method is a method of synthesizing lithium, silicon, and other simple substances such as metal elements or non-metal elements or their compounds in a predetermined molar ratio, and heating in air or in an atmosphere containing oxygen. Is. The respective compounds of lithium and silicon and other metal elements or non-metal elements as starting materials,
Any oxide, hydroxide, salt such as carbonate or nitrate, or organic compound may be used as long as it is a compound that is heated in air or in an atmosphere containing oxygen to form an oxide.

Each compound of lithium and silicon
Various oxides, hydroxides or other compounds containing oxygen
When using, non-oxidizing in an inert atmosphere or in a vacuum, etc.
Synthesis in a neutral atmosphere or in an atmosphere with a controlled amount of oxygen
It is also possible to do so. Among these starting materials,
Lithium oxide Li as a compound of um₂ O, peroxide
Tium Li₂ O₂, Lithium hydroxide LiOH, Lithium carbonate
Um Li₂ CO₃ , Lithium nitrate LiNO₃ And so on, Kay
Silicon dioxide as the elemental compound SiO₂ And Kay monoxide
Silicon oxides such as elemental SiO and their hydrates and orthoke
Formic acid H_Four SiO _Four, Metasilicic acid H₂ SiO₃ , Meta
Formic acid H₂ Si₂ O_Five And other silicic acids such as silicic acid
Etc. are easily decomposed by heating and easily form an oxide, and
It is particularly preferable because it easily forms a solid solution.

Further, these starting materials are water, alcohol,
It is also possible to dissolve or disperse in a solvent such as glycerin, uniformly mix and / or react in the solution, then dry and perform the above heat treatment. In particular, according to the method of heating the above-mentioned silicic acid or silicon oxide or an aqueous solution thereof as described above by adding a predetermined amount to an aqueous solution of lithium hydroxide, dissolving the resulting mixture, and drying and dehydrating the reaction product. There is an advantage that a uniform product can be obtained by heat treatment at a lower temperature. Although the heating temperature varies depending on the starting material and the heating atmosphere, it is usually possible to synthesize at 400 ° C. or higher, and preferably 800
C. or higher, more preferably 1100.degree. C. or higher.
Examples of lithium-containing silicon oxides obtained by heat treatment of such a mixture of a lithium compound and a silicon compound include Li ₄ SiO ₄ and Li ₂ SiO
₃ , Li ₂ Si ₂ O ₅ , Li ₄ Si ₃ O ₈ , Li ₆ Si ₄
Examples include various lithium silicates such as O ₁₁ and condensates thereof, and non-stoichiometric compositions in which lithium is in excess or deficiency with respect to these stoichiometric compositions.

Further, when various silicic acids such as those mentioned above are used as the starting compound of silicon or lithium hydroxide or the like is used as the lithium compound, hydrogen is not completely desorbed by the heat treatment. It is also possible that a part of the product remains after the heat treatment and lithium and hydrogen coexist, which are included in the present invention. Further, at the same time with lithium or a compound thereof, other alkali metals such as sodium, potassium and rubidium, alkaline earth metals such as magnesium and calcium and / or iron, nickel, manganese, vanadium,
Other metals such as titanium, lead, aluminum, germanium, boron, phosphorus, etc., other than lithium, are also added by adding other metals or non-metal elements such as simple substances or their compounds and mixing them with silicon or its compounds and heat-treating. Ions or non-metals can coexist with lithium ions and silicon, and these cases are also included in the present invention.

The lithium-containing silicon oxide or silicate thus obtained can be used as a negative electrode active material as it is or after being subjected to processing such as pulverizing and granulating if necessary. In addition, as in the case of the second method described below, the lithium-containing substance is contained by the electrochemical reaction between the lithium-containing silicon oxide or silicate and lithium or the lithium-containing substance. Increasing or decreasing the amount of lithium by causing the silicon oxide or silicate to further occlude lithium ions, or conversely, to release the lithium ions from the lithium-containing silicon oxide or silicate. You may use a thing as a negative electrode active material.

The second method is a silicon oxide such as silicon dioxide SiO ₂ or silicon monoxide SiO, or CaSi.
Containing lithium by occluding lithium ions in an oxide or silicate of silicon by an electrochemical reaction between a silicate such as O ₃ , MgSiO ₃ and Zn ₂ SiO ₄ and a substance containing lithium or lithium This is a method of obtaining an oxide or silicate of silicon. As the silicate, various synthetic silicates obtained from minerals can be used in addition to the artificially synthesized one obtained by the above-mentioned first method.

As the substance containing lithium for use in the electrochemical reaction, for example, a lithium ion which is used for the positive electrode active material or the negative electrode active material mentioned in the above-mentioned section of the prior art can be occluded. A releasable active material can be used. The storage of lithium ions by the electrochemical reaction of silicon into an oxide or silicate can be performed in the battery after the battery is assembled or inside or outside the battery during the battery manufacturing process. Can be done as follows.

That is, (1) one of the electrodes (working electrode) is formed by molding the silicon oxide or the silicate or a mixture of the silicon oxide or the silicate or the conductive agent and the binder into a predetermined shape. Metal lithium or a substance containing lithium is used as the other electrode (counter electrode) in contact with a lithium ion conductive non-aqueous electrolyte so that both electrodes face each other to form an electrochemical cell, and the working electrode is in the direction of cathodic reaction. A lithium ion is electrochemically occluded in the silicon oxide or the silicate by applying an appropriate current. A non-aqueous electrolyte secondary battery is constructed by using the obtained working electrode as it is as a negative electrode or as a negative electrode active material constituting the negative electrode.

(2) The silicon oxide or the silicate or a mixture of the silicon oxide or the silicate or the conductive agent and the binder is molded into a predetermined shape, and lithium or a lithium alloy or the like is pressure-bonded thereto. Alternatively, a laminated electrode that is brought into contact with one another is incorporated into a non-aqueous electrolyte secondary battery as a negative electrode. A method of forming a kind of local battery by touching the electrolyte with this laminated electrode in the battery and self-discharging to electrochemically occlude lithium in the oxide or silicate of silicon.

(3) A non-aqueous electrolyte secondary battery using the silicon oxide or the silicate as a negative electrode active material and using a material containing lithium and capable of inserting and extracting lithium ions as a positive electrode active material. . A method in which lithium ions released from the positive electrode by being charged when used as a battery are occluded in the silicon oxide or silicate.

The lithium-containing silicon oxide or silicate thus obtained is used as the negative electrode active material. The present inventors have also found that the chemical composition of the above-mentioned lithium-containing silicon oxide, in particular, the ratio of the number of oxygen atoms to the number of silicon atoms of electrochemical storage and release of lithium ions in a non-aqueous electrolyte. It has been found that it has a significant influence on the performance, that is, the charge / discharge performance.

As silicon oxide, silicon dioxide S
iO ₂ is the most stable and is well known in the form of quartz crystal, amorphous silica (glass) and the like. A lower oxide of silicon or a lithium-containing compound thereof having a smaller ratio of the number of oxygen atoms than silicon dioxide SiO ₂ or lithium silicate Li ₂ SiO ₃ having a ratio of the number of oxygen atoms to the number of silicon atoms of 2 or more. Li _x SiO _y (where x ≧
0, 2>y> 0) has a remarkably large amount that can electrochemically store and release lithium ions in the non-aqueous electrolyte, that is, a charge / discharge capacity, and its potential is 1. It was found that the charge / discharge capacity in a base region of 0 V or less was remarkably large and it was more excellent as the negative electrode active material. In particular, the lower oxide of silicon having an amorphous structure or a lithium-containing compound thereof has a large charge / discharge capacity, and is excellent in less deterioration due to repeated charge / discharge (cycle) or overcharge / discharge. I understood.

Based on these facts, the present invention further provides
As a negative electrode active material for this type of battery, more preferably, a novel compound having a composition formula of Li _x SiO _y (where x ≧ 0, 2>y> 0) and comprising a lithium-containing silicon oxide is used. It proposes to use a lithium ion storage / release material. That is, an oxide having a composition in which the ratio y of the number of oxygen atoms to the number of silicon atoms is less than 2 and greater than 0, contains lithium in its crystal structure, more preferably in its amorphous structure, and is non-aqueous. A lower oxide of silicon that can store and release lithium ions by an electrochemical reaction in an electrolyte is used. The state of lithium in this oxide is preferably mainly ionic, but is not necessarily limited.

The lower oxide Li _x SiO of silicon containing lithium used as the negative electrode active material of the battery of the present invention.
_As a preferable manufacturing method of _y (however, x ≧ 0, 2>y> 0), the following two kinds of methods are mentioned, but not limited thereto. The first method is a lower silicon oxide SiO _y (2>y> 0) which does not contain lithium in advance.
And a lithium ion is occluded in the lower oxide SiO _y of silicon by an electrochemical reaction between the obtained lower oxide SiO _{y of} silicon and lithium or a substance containing lithium to contain lithium. Is a method of obtaining a lower oxide of silicon, Li _x SiO _y . As such a lower oxide SiO _y of silicon, SiO _1.5 (Si ₂ O
₃ ), SiO _1.33 (Si ₃ O ₄ ), SiO and SiO
_In addition to the stoichiometric composition such as _0.5 (Si ₂ O), any composition in which y is larger than 0 and smaller than 2 may be used.

Also, these lower oxides of silicon SiO _y
Can be produced by various known methods as described below. That is, (1) a method in which silicon dioxide SiO ₂ and silicon Si are mixed at a predetermined molar ratio and heated in a non-oxidizing atmosphere or in a vacuum, (2) silicon dioxide SiO ₂ is a reducing gas such as hydrogen H _2. A method of heating in a predetermined amount to reduce a predetermined amount, (3) a method of mixing silicon dioxide SiO ₂ with a predetermined amount of carbon C or a metal, and heating to reduce a predetermined amount, (4) an oxygen gas or oxidation of silicon Si A method of heating an object to oxidize it by a predetermined amount, (5) a CVD method or a plasma CVD method in which a mixed gas of a silicon compound gas such as silane SiH ₄ and oxygen O ₂ is heated or plasma-decomposed.

On the other hand, as the substance containing lithium for use in the electrochemical reaction, for example, a lithium ion which is used in the positive electrode active material or the negative electrode active material mentioned in the section of the prior art mentioned above is occluded. A releasable active material can be used. The absorption of lithium ions by the electrochemical reaction of the silicon to the lower oxide SiO _y can be performed in the battery after the battery is assembled, or in the battery or outside the battery during the battery manufacturing process. Can be done as follows.

That is, (1) one of the electrodes (working electrode) is formed by molding a lower oxide of silicon or a mixture of the lower oxide of silicon and a conductive agent, a binder or the like into a predetermined shape, and metal lithium or lithium is used. Substance containing the other electrode (counter electrode)
As an electrochemical cell with both electrodes facing each other in contact with a lithium ion conductive non-aqueous electrolyte, the working electrode is energized with an appropriate current in the direction of cathodic reaction to electrochemically ionize the lithium ions of the silicon Store in lower oxide. A non-aqueous electrolyte secondary battery is constructed by using the obtained working electrode as it is as a negative electrode or as a negative electrode active material constituting the negative electrode.

(2) A lower oxide of silicon or a mixture of the lower oxide of silicon and a conductive agent or a binder is molded into a predetermined shape,
Lithium or an alloy of lithium or the like is pressure-bonded or brought into contact therewith to form a laminated electrode, which is incorporated as a negative electrode in a non-aqueous electrolyte secondary battery. A method of forming a kind of local battery by exposing the laminated electrode to the electrolyte in the battery, and self-discharging to electrochemically occlude lithium in the lower oxide of silicon.

(3) A non-aqueous electrolyte secondary battery is constructed using the lower oxide of silicon as a negative electrode active material and a material containing lithium and capable of inserting and extracting lithium ions as a positive electrode active material. A method in which lithium ions released from the positive electrode by being charged when used as a battery are occluded in the lower oxide of silicon.

The second method is a method of synthesizing each element of lithium and silicon or their compounds in a predetermined molar ratio, and heating in a non-oxidizing atmosphere or an oxygen-controlled atmosphere. . The respective compounds of lithium and silicon, which are the starting materials, are heated in a non-oxidizing atmosphere such as oxides, hydroxides, salts such as carbonates and nitrates, or organic compounds to form oxides. Compound is good. In particular, the lower oxide SiO _y of silicon shown in the above first method is used as a compound of silicon, and these are mixed with lithium or a compound having oxygen of lithium, and heated in an inert atmosphere or in a vacuum. The method is preferable because it is easy to control, easy to manufacture, and excellent in charge / discharge characteristics.

Further, these starting materials may be water or alcohol,
It is also possible to dissolve or disperse in a solvent such as glycerin, uniformly mix and / or react in the solution, then dry and perform the above heat treatment. In particular, it depends on the method of adding the predetermined amount of silicon or the above-mentioned lower oxide of silicon or a dispersion or aqueous solution thereof to an aqueous solution of lithium hydroxide and mixing them, drying and dehydrating the reacted product, and then performing the heat treatment described above. For example, a more uniform product can be obtained by heat treatment at a lower temperature. Although the heating temperature differs depending on the starting material and the heating atmosphere, it is usually possible to synthesize at 400 ° C. or higher,
On the other hand, at a temperature of 800 ° C. or higher, a disproportionation reaction of silicon Si and silicon dioxide SiO ₂ may occur, so 400-80
A temperature of 0 ° C. is preferred.

Further, when various silicic acids having hydrogen as a silicon compound are used as a starting material, or when lithium hydroxide or the like is used as a lithium compound, hydrogen is not completely desorbed by heat treatment, It is possible that a part of the product remains after the heat treatment and lithium and hydrogen coexist, which is included in the present invention. Further, together with lithium or a compound thereof and silicon or a compound thereof, a small amount of another alkali metal such as sodium, potassium or rubidium, an alkaline earth metal such as magnesium or calcium and / or iron, nickel, manganese, vanadium, titanium or lead. , Aluminium, germanium, boron, phosphorus and other metals or non-metal elements such as simple substances or compounds thereof are also mixed and heat-treated to remove a small amount of these metals or non-metals other than lithium from lithium and It can be made to coexist with silicon, and these cases are also included in the present invention.

The thus obtained lithium-containing silicon lower oxide can be used as a negative electrode active material as it is or after being optionally subjected to processing such as pulverization and granulation. In the same manner as in the first method, the lithium-containing silicon lower oxide is converted to the lithium-containing silicon lower oxide by an electrochemical reaction between the lithium-containing silicon lower oxide and lithium or a lithium-containing substance. Further, a material in which the amount of lithium is increased or decreased by occluding lithium ions or conversely releasing lithium ions from the lower oxide of silicon containing lithium may be used as the negative electrode active material.

It contains lithium thus obtained
Lower oxide of silicon Li_x SiO_yAs the negative electrode active material
To use. On the other hand, as the positive electrode active material, as described above, TiS
₂ , MoS₂ , NbSe₃ Metal chalcogenides such as
MnO₂ , MoO₃ , V₂ O_Five , Li_X CoO₂ , Li
_XNiO₂ , Li_x Mn₂ O_Four Metal oxides such as polyurea
Niline, polypyrrole, polyparaphenylene polyacene
Such as conductive polymers, graphite intercalation compounds, etc.
Each capable of occluding and releasing lithium ions and / or anions
Seed materials can be used. Including the lithium of the present invention
Having oxides of silicon, especially lower oxides Li _x SiO_y 
Negative electrode with a negative electrode active material is an electrode for metallic lithium.
Charging / discharging capacity in a low potential (base) and base area of 1 V or less
Has the advantage that the
For metallic lithium such as oxides and chalcogenides
The electrode potential with respect to it is 2 V or more, more preferably V₂ O_Five ,
MnO₂ , Li_X CoO₂ , Li_x NiO₂ And Li_x M
n₂ O_Four Have a high potential of 3V to 4V or more like etc.
By combining with a positive electrode using a (noble) active material
Higher voltage and energy density and excellent charge / discharge characteristics.
It is possible to obtain an improved secondary battery.

In particular, the composition formula is shown as Li _a M _b L _c O ₂ together with the negative electrode using the negative electrode active material comprising the lithium-containing silicon oxide or silicate according to the present invention, where M Is a transition metal element, L is one or more kinds of metal elements selected from boron B and silicon Si, and a, b,
c is 0 <a ≦ 1.15, 0.85 ≦ b + c ≦, respectively
1.3, 0 ≦ c, and when used in combination with a positive electrode using a positive electrode active material made of a composite oxide containing lithium and having a layered structure, the charge and discharge characteristics are particularly excellent at high energy density. At the same time, a secondary battery which is less deteriorated due to overcharge and overdischarge and has a long cycle life is particularly preferable.

The composite oxide Li _a M _b L _c O ₂ used as the positive electrode active material of the battery of the present invention can be synthesized as follows. That is, lithium Li, transition metal M and element L each alone or mixed with respective oxides, hydroxides or salts such as carbonates and nitrates at a predetermined ratio and heated in air or in an atmosphere containing oxygen at 600 ° C. or higher. It is obtained by heating and calcining at a temperature, preferably 700 to 900 ° C. When the oxides or compounds containing oxygen are used as the supply sources of Li, M, L and the like, it is possible to perform heat synthesis in an inert atmosphere. A heating time of 4 to 50 hours is usually sufficient, but it is effective to repeat the processes of firing, cooling, and pulverizing and mixing several times in order to promote the synthesis reaction and enhance the uniformity.

In the composition formula Li _a M _b L _c O ₂ , the standard Li ratio a is 1 in the above heat synthesis, but a non-stoichiometric composition of about ± 15% is also possible. It is possible, and 0 <a ≦ 1.15 is possible by electrochemical intercalation, deintercalation, or the like. Transition metal M
As the above, Co, Ni, Fe, Mn, Cr, V and the like are preferable, and Co and Ni are particularly preferable because they have excellent charge and discharge characteristics. Amount c of boron and / or silicon and amount b of transition metal M
When 0 <c and 0.85 ≦ b + c ≦ 1.3, the effects on reduction of polarization (internal resistance) during charge / discharge, improvement of cycle characteristics, etc. are remarkable, which is preferable. On the other hand, the charge / discharge capacity in each cycle decreases conversely when the amount c of boron and / or silicon is too large, and becomes the maximum when 0 <c ≦ 0.5. Therefore, this range is particularly preferable.

As the electrolyte, γ-butyrolactone, propylene carbonate, ethylene carbonate,
LiClO ₄ , LiPF ₆ , LiBF ₆ as a supporting electrolyte in a single or mixed solvent of organic solvents such as butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl formate, 1,2-dimethoxyethane, tetrahydrofuran, dioxolane and dimethylformamide.
₄ , a non-aqueous (organic) electrolytic solution in which a lithium ion dissociable salt such as LiCF ₃ SO ₃ is dissolved, a polymer solid electrolyte in which the lithium salt is dissolved in a polymer such as polyethylene oxide or a crosslinked polyphosphazene, or Li ₃ N, LiI
Lithium ion conductive non-aqueous electrolytes such as inorganic solid electrolytes and the like can be used.

However, the oxide of silicon containing lithium according to the invention, in particular the lower oxide of silicon Li _x Si.
When O _y is used as the negative electrode active material and a non-aqueous electrolyte secondary battery is constructed using the above non-aqueous electrolyte, the difference between the charge capacity and the discharge capacity, that is, the capacity loss remarkably differs depending on the type of the non-aqueous electrolyte used. It was also found that the charging and discharging efficiencies were remarkably different, and therefore the discharge capacity was decreased by repeated charging and discharging, and thus the cycle life was remarkably different. The main reason for this will be described in detail in Examples described later, but in a negative electrode using an oxide of silicon containing lithium, particularly a lower oxide of silicon Li _x SiO _y as an active material during charging, a non-aqueous electrolyte is It was clarified that this was because the non-aqueous electrolyte was deteriorated due to decomposition and gas generation, and the internal resistance was increased. The generation of gas due to the decomposition of the electrolytic solution raises the internal pressure of the battery, and in extreme cases, it may cause the battery to swell, leading to rupture, which is an important safety issue. If such a battery is actually installed in an electronic device or the like and used, the electronic device may be damaged.

Generally, the non-aqueous electrolyte is also oxidized / reduced by an electrochemical reaction when a high potential or a low potential outside the stable region is applied. As a result, the electrolytic solution is decomposed and deteriorated, which leads to deterioration of the battery and shortening of the charge / discharge cycle life when used as a battery. In particular, Li _x SiO of the present invention
_When a lithium-containing lower oxide of silicon represented by _y (0 ≦ x, 0 <y <2) is used as the negative electrode active material, the non-aqueous state is more preferable than the deterioration of the active material itself due to repeated charging and discharging. The internal resistance of the battery increases due to the accumulation of gas generated by the deterioration and decomposition of the electrolytic solution, which causes the performance of the battery to deteriorate. In addition, the above-mentioned capacity loss is large, and the high charge / discharge capacity characteristic of the active material cannot be fully utilized.

In order to solve the above-mentioned problems, the present invention is also represented by an oxide of silicon containing lithium as a negative electrode active material, particularly Li _x SiO _y (0 ≦ x, 0 <y <2). It is proposed to use a non-aqueous electrolyte containing ethylene carbonate (EC) in a secondary battery using a lower oxide. Since EC has a high freezing point, it is desirable to set the volume ratio to 80% or less with respect to the total solvent of the electrolytic solution. Further, since EC is a highly viscous solvent, it must also contain an R · R ′ type alkyl carbonate (including R = R ′) represented by Formula 1 in order to further enhance ionic conductivity and further stabilize it. Is desirable. R and R ′ are alkyl groups represented by C _n H _{2n + 1} , and when n = 1, 2, 3, 4, 5, particularly high ionic conductivity and low viscosity are preferable. Among them, dimethyl carbonate (DM) in which R and R'in Formula 1 are a methyl group (n = 1) or an ethyl group (n = 2)
C), diethyl carbonate (DEC), methyl ethyl carbonate and the like are more preferable. Further, it is desirable to compose the solvent of the electrolytic solution with EC and the R / R'-type alkyl carbonate represented by the formula 1. When the mixing ratio of EC and the R / R'-type alkyl carbonate is about 1: 1 by volume. Since the ionic conductivity is maximum, the mixing ratio is about 3: 1 by volume.
The ratio of 1: 3 is particularly preferable.

As described above, the supporting electrolyte in the electrolytic solution is a salt that dissociates Li ⁺ ions in the solvent and is used as a negative electrode.
Any material that does not directly chemically react with the positive electrode may be used, for example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ S.
O ₃ , Li (CF ₃ SO ₂ ) ₂ N, etc. are preferable.

[0043]

The negative electrode using the lithium-containing silicon oxide or silicate of the present invention as the negative electrode active material is stable in the non-aqueous electrolyte in the range of an electrode potential of at least 0 to 3 V with respect to metallic lithium. It can repeatedly occlude and release lithium ions, and can be used as a negative electrode of a secondary battery that can be repeatedly charged and discharged by such an electrode reaction. In particular, in a base potential region of 0 to 1 V with respect to the lithium reference electrode (metal lithium), it has a high-capacity charging / discharging region capable of stably occluding / releasing lithium ions and repeatedly charging / discharging.
Further, as compared with a carbonaceous material such as graphite which has been conventionally used as a negative electrode active material of this type of battery, an amount capable of reversibly occluding and releasing lithium ions, that is, an effective charge / discharge capacity is remarkably large and polarization of charge / discharge is small. Therefore, charging / discharging with a large current is possible, and deterioration such as generation of an irreversible substance due to overcharging / overdischarging is hardly seen, and an extremely stable secondary battery having a long cycle life can be obtained.

In particular, a lower oxide Li _{x of} silicon having a composition in which the ratio y of the number of oxygen atoms to the number of silicon atoms is less than 2.
When SiO _y (where x ≧ 0, 2>y> 0) is used, when a silicon oxide or silicate having a ratio y of the number of oxygen atoms to the number of silicon atoms of 2 or more is used. In comparison, an amount capable of reversibly occluding and releasing lithium ions, that is, an effective charge / discharge capacity is remarkably large, and a secondary battery having particularly excellent charge / discharge characteristics can be obtained.

Further, in the negative electrode active material made of a lithium-containing silicon oxide or silicate according to the present invention, a lithium ion absorption and desorption reaction at a temperature below the melting point (about 180 ° C.) of lithium metal. Since it has a sufficiently high battery reaction rate, it is particularly suitable for a non-aqueous electrolyte secondary battery that operates at room temperature or at room temperature.

The reason why such excellent charge and discharge characteristics are obtained is not always clear, but it is presumed as follows. That is, a novel oxide or silicate of silicon containing lithium, which is a novel anode active material according to the present invention, has a basic structure in which a silicon atom having a strong covalent bond and an oxygen atom are coordinated with the oxygen atom centered around the silicon atom. Form a chain structure, a layered structure, a three-dimensional network structure, etc. that form a skeleton structure in a continuous manner, and the mobility of lithium ions in such a structure is high, and there are many sites that can store lithium ions. Therefore, it is presumed that it is easy to insert and extract lithium ions.

Further, in an oxide or silicate of silicon having a ratio y of the number of oxygen atoms to the number of silicon atoms of 2 or more, a skeleton structure in which a tetrahedron in which silicon atoms and four oxygen atoms are bonded is connected, On the contrary, Li _x Si in which y is 0 has a skeleton structure composed of only silicon-bonded bonds, whereas Li _x S, a lower oxide of silicon containing lithium, Li _x S
iO _y (where x ≧ 0, 2>y> 0) forms a skeleton structure having a bond between silicon atoms and oxygen atoms as well as a bond between silicon atoms, and particularly lithium in such a structure. It is presumed that the ion mobility is high and the number of sites that can store lithium ions is very large, so that the lithium ions can be easily stored and released.

On the other hand, the complex oxide Li _a M _b L _c O ₂ used as the positive electrode active material has a high potential of about 4 V or higher with respect to metallic lithium and has at least 0 <a ≦ 1. Between 15 and 15, reversible charge and discharge by Li ion intercalation and deintercalation are possible, deterioration by overcharge and overdischarge is small, and excellent cycle characteristics are obtained. Especially B and / or S
When the content c of i is 0.05 ≦ c <0.5, the polarization is small and the cycle characteristics are excellent. The reason why such excellent charge / discharge characteristics are obtained is not always clear, but it is presumed as follows. That is, the positive electrode active material Li _a M _b L _c O ₂ according to the present invention is α-N containing neither B nor Si.
α-NaCr in which a part of the transition metal element M of the aCrO ₂ type layered structure Li _a M _b O ₂ is replaced with B or Si
It has a skeletal structure similar to that of the O ₂ type. However, B atoms and Si atoms may also be present in interstitial gaps of crystals and Li sites (replaced with Li). In any case, the crystal structure and electronic structure change due to the presence of B or Si.
It is presumed that this is because the ionic conductivity is enhanced and the occlusion / release of lithium ions is facilitated.

Therefore, the battery using the negative electrode active material and the positive electrode active material according to the present invention in combination has a voltage of about 4V.
It has a high operating voltage, is reversibly capable of occluding and releasing lithium ions, that is, the charging / discharging capacity is remarkably large, and the polarization of charging / discharging is small. Degradation of the active material due to discharge, deterioration such as crystal collapse, etc. is hardly seen, and extremely stable and long cycle life, etc., and particularly excellent performance.

Further, in the non-aqueous electrolyte secondary battery of the present invention using a lithium-containing silicon oxide as a negative electrode active material, EC or an RR 'type alkyl carbonate represented by Formula 1 is contained as an electrolyte. By using the non-aqueous electrolyte, it is possible to remarkably suppress the decomposition of the electrolyte during charge / discharge and the deterioration due to gas generation. That is, a non-aqueous electrolytic solution prepared by dissolving LiClO ₄ , LiPF ₆ or the like as a supporting electrolyte in PC, which has been most commonly used in conventional non-aqueous electrolyte secondary batteries of the type described above, is treated with the above-mentioned lithium-containing silicon. Oxides, especially lower oxides of silicon Li _x SiO _y
When (0 <y <2) is used in a battery having a negative electrode active material, gas is violently generated due to decomposition of the electrolytic solution during charging,
Although the discharge capacity decreases remarkably due to repeated charging and discharging, an electrolyte containing EC, especially EC and DEC or DM
LiClO ₄ or LiP as a supporting electrolyte in a mixed solvent of C
When an electrolytic solution in which F ₆ or the like is dissolved is used, decomposition of the electrolytic solution or gas generation does not occur. As a result, the capacity loss during charge and discharge is significantly reduced, the charge and discharge efficiency is significantly improved, and the high capacity density inherent in the active material of the negative and positive electrodes is utilized to achieve high voltage, high energy, long cycle life, and long reliability. You can get a high battery.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0052]

EXAMPLE FIG. 1 is a cross-sectional view of a coin-type battery showing an example of a test cell used for performance evaluation of a negative electrode active material of a non-aqueous electrolyte secondary battery according to the present invention in the following examples. . In the figure, reference numeral 1 is a counter electrode case which also serves as a counter electrode terminal, which is obtained by drawing a stainless steel plate having Ni plated on one outer surface. Reference numeral 2 denotes a counter electrode current collector made of a stainless steel net, which is spot-welded to the counter electrode case 1. The counter electrode 3 is an aluminum plate having a predetermined thickness and a diameter of 15 m.
m is punched out, fixed to the counter electrode current collector 2, and a lithium foil having a predetermined thickness punched out to a diameter of 14 mm is press-bonded thereon. Reference numeral 7 denotes a working electrode case made of stainless steel whose outer surface is plated with Ni, and also serves as a working electrode terminal. Reference numeral 5 is a working electrode composed of an active material according to the present invention or a comparative active material according to a conventional method described later, and 6 is a net made of stainless steel or a conductive adhesive containing carbon as a conductive filler. Working electrode current collector, working electrode 5
And the working electrode case 7 are electrically connected. 4 is a separator made of a polypropylene porous film, which is impregnated with an electrolytic solution. Numeral 8 is a gasket mainly composed of polypropylene, which is interposed between the counter electrode case 1 and the working electrode case 7 to maintain the electrical insulation between the counter electrode and the working electrode, and at the same time the working electrode case opening edge is inward. By folding and crimping, the battery contents are hermetically sealed. The battery has an outer diameter of 20 mm and a thickness of 1.
It was 6 mm.

(Embodiment 1) The working electrode 5 of this embodiment is as follows.
Was prepared. Commercially available lithium metasilicate Li ₂ Si
O₃ Was crushed and sized by an automatic mortar to a particle size of 53 μm or less.
The active material a according to the present invention is used as a conductive agent.
Crosslinking acrylic resin etc. using graphite as a binder
In a weight ratio of 30: 65: 5 and a working electrode mixture.
And then apply this working mixture from a stainless steel net.
With a working electrode current collector 6 of 2 ton / cm2 and a diameter of 15
20 mm after being pressed into pellets with a thickness of 0.5 mm
What was dried under reduced pressure at 0 ° C. for 10 hours was used as a working electrode.

For comparison, the above-mentioned book is used except that the same graphite as that used for the above-mentioned conductive material is used as an active material (abbreviated as active material r) instead of the above-mentioned active material a according to the present invention. A similar electrode (working electrode for comparison) was prepared in the same manner as the working electrode of the invention. The electrolytic solution used was a solvent in which propylene carbonate and 1,2-dimethoxyethane were mixed at a volume ratio of 1: 1 and lithium perchlorate LiClO ₄ was dissolved at 1 mol / l.

The battery thus manufactured has a temperature of 1 at room temperature.
After being left to stand for a week, it was subjected to the charge / discharge test described below. By this aging, the lithium-aluminum laminated electrode of the counter electrode is sufficiently alloyed by touching the non-aqueous electrolyte in the battery, and the lithium foil is substantially all Li-Al alloy. 0.4V compared with the case where metallic lithium is used alone as
It became a lowered value and became stable.

The batteries thus produced will be abbreviated as batteries A and R, corresponding to the active materials a and r of the working electrodes used. 0.4 mA for these batteries A and R
With a constant current of, the end voltage of charging (current direction in which the battery reaction in which lithium ions are occluded from the electrolyte to the working electrode)
Final voltage of 0.4 V, discharge (direction of current causing battery reaction in which lithium ions are released from working electrode into electrolyte) 2.
FIG. 2 shows the charging characteristics of the third cycle when the charging / discharging cycle was performed under the condition of 5 V, and FIG. 3 shows the discharging characteristics. or,
FIG. 4 shows the charging characteristics of the third cycle when the charging / discharging cycle is performed under the conditions of the same constant current, the charging end voltage is −0.8 V and the discharging end voltage is 2.5 V, and FIG.
Further, FIG. 6 shows the cycle characteristics. The charging / discharging cycle started from charging. After these charge / discharge cycles, when the battery in the charged state and the discharged state was disassembled and observed under a microscope, no precipitation of lithium metal was observed on the working electrode, and the charge / discharge reaction of the working electrode was substantially activated. It was confirmed that the reaction was caused by the substance.

As is apparent from FIGS. 2 to 6, the charge / discharge capacity of the battery A according to the present invention is significantly larger than that of the comparative battery R, and the reversible charge / discharge region is significantly expanded.
Further, it can be seen that the difference in operating voltage between charging and discharging is extremely small over the entire charging / discharging region, the polarization (internal resistance) of the battery is extremely small, and large current charging / discharging is easy. Further, the decrease in discharge capacity (cycle deterioration) due to repeated charging and discharging is extremely small. As described above, in the silicon-containing oxide or silicate containing lithium which is the active material of the working electrode of the battery A according to the present invention as described above, four oxygen atoms are bonded centering on the silicon atom. It has a skeleton structure in which tetrahedra are connected, the mobility of lithium ions in this structure is high, and because there are many sites that can store lithium ions, it is easy to store and release lithium ions. Presumed.

(Example 2) Instead of the active material a of Example 1, a commercially available reagent grade grade silicon dioxide SiO _{2 was used.}
The (precipitated silicic acid anhydride) was pulverized and sized to a particle size of 53 μm or less and used as the active material (abbreviated as active material b) of the working electrode. A weight ratio of the active material b, the same graphite as used in Example 1 as a conductive agent, and the same cross-linked acrylic acid resin as used in Example 1 as a binder, in a weight ratio of 30:65:
5 at a ratio of 5 to form a working electrode mixture, and then this working electrode mixture is mixed with a working electrode current collector 6 made of a stainless steel net into pellets having a diameter of 15 mm and a thickness of 0.5 mm at ² ton / cm ^2. After pressure molding, the product was dried under reduced pressure at 200 ° C. for 10 hours and used as a working electrode. A similar battery B was manufactured in the same manner as in Example 1 except that the working electrode thus manufactured was used.

The battery B thus obtained was also subjected to the same charge / discharge cycle test as in Example 1. The results at this time are also shown in FIGS.
As is apparent from the figure, the battery B of this example has the same excellent charge / discharge characteristics as the battery A of the first example according to the present invention. That is, lithium ions are released from the Li-Al alloy of the counter electrode into the electrolytic solution due to charging, and the lithium ions move in the electrolytic solution to cause an electrode reaction with the active material b, and the active material b is electrochemically reacted. Lithium ions are occluded and a silicon oxide containing lithium is produced. Next, during discharge, lithium ions are released from this oxide into the electrolytic solution, move in the electrolytic solution, and are occluded in the Li-Al alloy of the counter electrode, so that stable charge and discharge can be performed repeatedly. Here, the active material b is a silicon-containing silicon oxide containing lithium after the first charging, and then a lithium-containing silicon oxide is oxidized in a subsequent discharge-charge cycle except during complete discharge. Is forming a thing.

Example 3 In this example, an active material synthesized as follows (abbreviated as active material c) was used in place of the active material a of Example 1, and the activity of the working electrode was A battery C was prepared in the same manner as in Example 1 except for the substances.

The active material c of this example was synthesized as follows. Lithium hydroxide LiOH ・ H ₂ O and silicon dioxide S
iO2 and the vanadium pentoxide _{V 2 O 5 Li: Si:} V
= 2: 0.9: 0.1 at a molar ratio of 1: 1 and thoroughly mixed in a mortar, and then the mixture was heated in the atmosphere at a temperature of 1000 ° C for 12 hours.
Heat treated for hours. After cooling, the product obtained has a particle size of 53
What was pulverized and sized to less than μm was used as the active material c in this example.

The battery C thus obtained was also subjected to the same charge / discharge cycle test as in Example 1. The results at this time are also shown in FIGS. 2 to 6, as in Examples 1 and 2. As is apparent from the figure, the battery C of this example has excellent charge / discharge characteristics as the batteries A and B of Examples 1 and 2 according to the present invention.

In addition, the active materials a, b and c of the batteries A, B and C according to the present invention have a negative electrode with respect to the Li-Al alloy electrode.
0.4 to + 0.6V (about 0 to 1V against metallic lithium)
(Corresponding to (1)), the charge and discharge capacities in the base potential region are remarkably large, which indicates that it is excellent as a negative electrode active material for a non-aqueous electrolyte secondary battery. In particular, the active material a of Example 1 using metasilicate as a starting material has a larger charge / discharge capacity in a base potential region and a base electric potential,
Particularly excellent as a negative electrode active material.

(Example 4) The working electrode 5 was prepared as follows. A silicon oxide or silicon Si represented by the composition number SiO _y (where 0 ≦ y) described later was pulverized and sized to a particle size of 53 μm or less by an automatic mortar and used as an active material of the working electrode. These active materials were mixed with the same graphite as that used in Example 1 as a conductive agent and a cross-linking acrylic resin as a binder at a weight ratio of 65:20:15 to prepare a working electrode mixture. . Next, 2 tons of this working electrode mixture
Working electrode 5 was produced by pressure molding into a pellet having a diameter of 15 mm and a thickness of 0.3 mm at n / cm ² . Thereafter, the working electrode 5 thus obtained is bonded to a working electrode case 7 by using a working electrode current collector 6 made of a conductive resin adhesive containing carbon as a conductive filler, and integrated at 200 ° C. The coin-type battery described above was prepared by using the dried product under reduced pressure for 10 hours.

As the active material of the working electrode, the above composition number S
Ratio y of number of oxygen atoms to number of silicon atoms in iOy y
Were compared using the following three types having a value of 2 to 0. That is,
(B1) Silicon dioxide SiO ₂ corresponding to y = 2 (the same commercial grade grade precipitated silicic anhydride, amorphous structure used in Example 1), (d1) monoxide corresponding to y = 1. Silicon SiO (commercial grade grade, amorphous structure),
(E) Three types of silicon Si (commercially available special grade) corresponding to y = 0.

The electrolyte used was a mixture of propylene carbonate, ethylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1: 2 in which 1 mol / l of lithium perchlorate LiClO ₄ was dissolved. The battery thus manufactured was left to stand for 1 week at room temperature and then subjected to the charge / discharge test described below. By this aging,
The lithium-aluminum laminated electrode of the counter electrode is sufficiently alloyed by touching the non-aqueous electrolyte in the battery, and the lithium foil is substantially all Li-Al alloy.
The battery voltage became stable at a value that was about 0.4 V lower than that when metal lithium was used alone as the counter electrode.

The batteries thus produced will be abbreviated as batteries B1, D1 and E below, corresponding to the active materials b1, d1 and e of the working electrodes used. These batteries B
1, D1 and E at a constant current of 1 mA, the end voltage of charging (current direction in which battery reaction in which lithium ions are occluded in the working electrode from the electrolyte) −0.4 V, discharge (lithium from working electrode to electrolyte) FIG. 7 shows the charge characteristics of the first cycle and FIG. 8 shows the discharge characteristics when the charge / discharge cycle is performed under the condition of a final voltage of 2.5 V (in the direction of the current in which the ions are discharged in the battery reaction). The charging / discharging cycle started from charging.

As is clear from FIGS. 7 and 8, the composition formula S
In a battery using a working electrode in which an oxide of silicon represented by iO _y is used as an active material, compared with battery B1 and battery E in which the ratio y of the number of oxygen atoms to the number of silicon atoms is 2 and 0, y is It can be seen that the charge / discharge capacity of the battery D1 having the intermediate value 0 <y <2 is remarkably large, and the reversible region of charge / discharge is remarkably expanded. Further, it can be seen that the difference in operating voltage between charging and discharging is extremely small over the entire charging / discharging region, the polarization (internal resistance) of the battery is extremely small, and large current charging / discharging is easy. In particular, -0.4 to +0.6 V with respect to the counter Li-Al alloy electrode (about 0 with respect to metallic lithium).
(Corresponding to ˜1 V), the charge and discharge capacities in a base potential region are remarkably large, and thus it is found that they are particularly excellent as a negative electrode active material for a non-aqueous electrolyte secondary battery.

That is, lithium ions are released from the Li-Al alloy of the counter electrode into the electrolyte due to charging, and the lithium ions move in the electrolyte to form the active material SiO _{y of the} working electrode.
And an electrode reaction with the active material SiOy to electrochemically occlude lithium ions and contain lithium oxide L of silicon
i _x SiO _y is generated. Next, during discharge, lithium ions are released from the oxide Li _x SiO _y into the electrolyte, move in the electrolyte, and are occluded in the Li-Al alloy of the counter electrode, whereby stable repeated charge and discharge can be performed. Here, after the active material SiO _y has produced a lithium-containing silicon oxide Li _x SiO _y by the first charge, it is charged with lithium except during complete discharge in the subsequent discharge-charge cycle. oxide Li _x 'Si of the silicon containing
Forming O _y . In such a lithium-containing silicon oxide Li _x SiO _y , the ratio y of the number of oxygen atoms to the number of silicon atoms of the oxide SiO _y (completely discharged state) in a state where lithium is completely released is silicon dioxide Si.
It can be seen that the charge / discharge characteristics are particularly excellent in the case of a lower oxide having a value 0 <y <2 which is an intermediate value between O ₂ and silicon simple substance. Also, it can be seen that the amorphous structure has excellent charge / discharge characteristics.

This is because the lower oxide SiO _y of silicon having the ratio y of the number of oxygen atoms to the number of silicon atoms of 0 <y <2 is as described above, in addition to the bond between the silicon atom and the oxygen atom. It forms a skeleton structure that has bonds between silicon atoms, it is easy to form a stable amorphous structure, the mobility of lithium ions in such a structure is high, and the sites that can store lithium ions are extremely It is presumed that it is easy to store and release lithium ions due to its large amount.

Example 5 In this example, an active material (abbreviated as active material f) synthesized as follows was used instead of the active material of the working electrode of Example 4, and the working electrode was used. A similar battery F was produced in the same manner as in Example 4 except for the active material in Example 4.

The active material of this example was synthesized as follows. Lithium hydroxide LiOH.H ₂ O and the same silicon monoxide SiO used in Example 4 were used as Li: Si = 1:
After thoroughly mixing with a mortar at a molar ratio of 1, this mixture was heat-treated in a nitrogen stream at a temperature of 700 ° C. for 12 hours. After cooling, the obtained product was pulverized and sized to a particle size of 53 μm or less and used as the active material f in this example. The active material f thus obtained had an average composition of LiSiO _1.5 , had a ratio y of the number of oxygen atoms to the number of silicon atoms of 1.5, and had a lower oxidation of silicon containing lithium in the structure in advance. It is a thing.

The battery F thus obtained was subjected to the same charge / discharge cycle test as in Example 4. The results at this time are also shown in FIGS.
As is apparent from the figure, the battery F of the present example is different from the battery B1 of Example 4 in which the ratio y of the number of oxygen atoms to the number of silicon atoms is 2 and the battery B1 using the silicon oxide SiO _2. Although the capacity is large and the charge / discharge characteristics are excellent, the charge / discharge capacity is small and the charge / discharge characteristics are inferior as compared with the battery D1 using the lower oxide SiO of silicon in which y is 1. Therefore, the ratio y of the number of oxygen atoms to the number of silicon atoms is 0.
It can be seen that <y <1.5 is particularly excellent.

Example 6 In this example, the same silicon monoxide SiO as that used in Example 4 was pulverized and sized to a particle size of 53 μm or less and used as the active material of the working electrode. This active material, the same graphite as used in Example 4 as a conductive agent, and the same cross-linking acrylic resin as used in Example 4 as a binder were mixed at a weight ratio of 30:55:15. After mixing to make a working electrode mixture, then this working electrode mixture 95m
g was pressed at ² ton / cm ² into a pellet having a diameter of 15 mm and a thickness of 0.3 mm to obtain a working electrode 5. A similar battery D2 was prepared in the same manner as in Example 4, except that the working electrode prepared in this manner was used.

As for the battery D2 thus obtained, the constant voltage of 1 mA was applied to the battery D2 as in Example 4, and the final voltage of charging-
A charge / discharge cycle test was performed under the conditions of 0.4 V and a discharge end voltage of 2.5 V. The charge / discharge characteristics of the third cycle at this time are shown in FIG. 9, and the cycle characteristics are shown in FIG.

As is clear from the figure, the charge / discharge capacity at the third cycle is a high capacity of 1100 mAh / g or more per 1 g of the active material SiO, and the operating voltage is 0.6 V ( Most of the base area is less than or equal to 1 V (corresponding to about 1 V with respect to metallic lithium), and reduction in discharge capacity (cycle deterioration) due to repeated charging and discharging is small, and the negative electrode activity of the non-aqueous electrolyte secondary battery is small. It turns out that it is particularly excellent as a substance.

Example 7 The state of gas generation during charge / discharge was observed for various non-aqueous electrolytes. A three-electrode glass electrochemical cell was used, and the counter electrode and the reference electrode were made of lithium metal. The working electrode was prepared as follows.
Silicon monoxide (Si
O), graphite as a conductive agent, and crosslinked acrylic acid resin as a binder in a weight ratio of 65:20:15.
After mixing into a working electrode mixture at a ratio of 2 ton / cm ² and press-molding into pellets having a diameter of 15 mm and a thickness of 0.3 mm,
What was vacuum-dried at 200 ° C. for 10 hours was used as a working electrode.
The electrolytes were compared using the six types shown in Table 1.

SiO is an electrolyte containing Li ions,
It is considered that Li ions are electrochemically intercalated and deintercalated to cause the reaction shown in Formula 2.

[0079]

[Equation 2]

While measuring the cyclic voltammogram (CV) in such a cell, the state of gas generation from the surface of the working electrode was observed. The voltage range of CV is 0-3V (vs
Li / Li ⁺ ), the scanning speed is 10 mV / sec,
Several scans were performed. Table 1 shows the state of gas generation obtained by the above measurement.

[0081]

[Table 1]

From Table 1, it is clear that the addition of EC to the electrolytic solution can remarkably suppress the generation of gas, and the addition of DEC to EC can suppress the generation of gas almost completely. . (Embodiment 8) In this embodiment, the coin-type battery shown in FIG. 1 is used to determine the charge / discharge cycle characteristics of the negative electrode active material of the non-aqueous electrolyte secondary battery according to the present invention depending on the difference in the non-aqueous electrolyte. This is a comparative evaluation of the difference. A similar battery was manufactured in the same manner as in Example 4, except that the working electrode 5 and the electrolytic solution were set as follows, and the thickness of the lithium-aluminum laminated electrode of the counter electrode 3 was increased by 1.5 times. The working electrode 5 was produced as follows. A weight ratio of silicon monoxide (SiO) crushed and sized to a particle size of 53 μm or less, graphite as a conductive agent, and a cross-linking acrylic resin as a binder is 30: 5.
The mixture is mixed at a ratio of 5:15 to make a working electrode mixture, 2 ton /
A working electrode 5 was obtained by pressure molding into a pellet having a diameter of 15 mm and a thickness of 0.15 mm in cm ² .

The following four kinds of electrolytic solutions were used for comparison. That is, (g) 1 mol / l of LiClO ₄ dissolved in a 1: 1 volume ratio PC / DME mixed solvent, (h) EC
1 mol / l of LiClO ₄ dissolved in a mixed solvent of 1: 1 by volume of DME and DME, (i) Volume ratio of EC and DEC of 1:
1 mol / l of LiClO ₄ dissolved in 1 mixed solvent,
(J) LiPF in a mixed solvent of EC and DEC at a volume ratio of 1: 1
There are four types of ₆ dissolved in 1 mol / l. The batteries prepared in this manner are described below in correspondence with the electrolytes g, h, i and j used. J
Is abbreviated.

The battery prepared as described above was charged with a constant current of 1 mA as in Example 4, and the final voltage of charging (current direction in which battery reaction in which lithium ions were occluded in the working electrode)-
FIG. 11 shows the charge characteristics of the fifth cycle when a charge / discharge cycle was performed under the conditions of 0.4 V and a final voltage of 2.5 V of discharge (current direction in which battery reaction in which lithium ions are released from the working electrode). The discharge characteristics are shown in FIG. 12, and the cycle characteristics of 1 to 10 cycles are shown in FIG. The charging / discharging cycle started from charging.

As is clear from FIGS. 11 to 13, the inclusion of EC in the electrolytic solution increased the charge / discharge capacity, reduced the capacity loss, and extended the charge / discharge cycle life. Further, when EC and DEC were used as the solvent of the electrolytic solution, a better result was obtained.

(Example 9) FIG. 14 is a sectional view of a coin-type battery showing an example of the non-aqueous electrolyte secondary battery according to the present invention. In the figure, reference numeral 11 denotes a negative electrode case which also serves as a negative electrode terminal, which is obtained by drawing a stainless steel plate having Ni plated on one outer surface. Reference numeral 13 denotes a negative electrode constituted by using a negative electrode active material according to the present invention described later, which is a negative electrode current collector 12 made of a conductive adhesive containing carbon as a conductive filler.
Is bonded to the negative electrode case 11. Reference numeral 17 denotes a positive electrode case made of stainless steel having one outer surface plated with Ni, which also serves as a positive electrode terminal. Reference numeral 15 is a positive electrode constituted by using a positive electrode active material according to the present invention, which will be described later, and is a positive electrode current collector 16 made of a conductive adhesive containing carbon as a conductive filler.
Is bonded to the positive electrode case 17. 14 is a separator made of a polypropylene porous film,
It is impregnated with electrolyte. Reference numeral 18 denotes a gasket mainly made of polypropylene, which is interposed between the negative electrode case 11 and the positive electrode case 17 to maintain the electrical insulation between the negative electrode and the positive electrode, and at the same time, the opening edge of the positive electrode case is bent inward. The battery contents are thus hermetically sealed. The electrolytic solution had a volume ratio of propylene carbonate, ethylene carbonate and 1,2-dimethoxyethane of 1:
Lithium perchlorate LiClO ₄ dissolved in a 1: 2 mixed solvent at 1 mol / l was used. Battery size is outer diameter 2
The thickness was 0 mm and the thickness was 1.6 mm.

The negative electrode 13 was manufactured as follows. Commercially available silicon monoxide SiO having a purity of 99.9% was pulverized and sized by an automatic mortar to have a particle size of 53 μm or less, which was used as a negative electrode active material according to the present invention, and graphite as a conductive agent was cross-linked as a binder. Type acrylic resin etc. weight ratio 65: 2
The mixture was mixed at a ratio of 0:15 to obtain a negative electrode mixture, and this negative electrode mixture was ² ton / cm ² and had a diameter of 15 mm and a thickness of 0.1.
A 9 mm pellet was press-molded and then dried under reduced pressure at 200 ° C. for 10 hours to obtain a negative electrode.

The positive electrode 15 was manufactured as follows. Lithium hydroxide LiOH.H ₂ O and cobalt carbonate CoCO ₃ were weighed so that the molar ratio of Li: Co was 1: 1 and sufficiently mixed using a mortar, and then this mixture was heated to 850 ° C. in the atmosphere.
It was heated and baked at the temperature of 12 hours, cooled, and then pulverized and sized to a particle size of 53 μm or less. This firing and crushing and sizing were repeated twice to synthesize the positive electrode active material LiCoO ₂ of this example.

This product was used as a positive electrode active material, graphite was mixed as a conductive agent, and fluorine resin or the like was mixed as a binder at a weight ratio of 80: 15: 5 to prepare a positive electrode mixture.
Next, this positive electrode mixture was treated at ² ton / cm ² and had a diameter of 16.2 m.
m after pressure molding into 0.71 mm thick pellets,
What was dried under reduced pressure at 0 ° C. for 10 hours was used as a positive electrode.

The battery thus produced (referred to as battery K) was left to stand for 1 week at room temperature and then subjected to the charge / discharge test described below. With this battery K at a constant current of 1 mA, the final voltage of charging was 4.4 V and the final voltage of discharging was 2.0 V.
FIG. 15 shows the charge / discharge characteristics of the first cycle and the second cycle when the charge / discharge cycle was carried out under the conditions of, and FIG. 16 shows the cycle characteristics. The charging / discharging cycle started from charging.

In this battery K, lithium ions are released from the positive electrode active material into the electrolytic solution due to charging, and the lithium ions move in the electrolytic solution to cause an electrode reaction with the negative electrode active material.
Lithium ions are electrochemically occluded in the negative electrode active material to form a composite oxide Li _x SiO of lithium and silicon.
Next, during discharge, lithium ions are released from the composite oxide of lithium and silicon of the negative electrode into the electrolytic solution, move in the electrolytic solution, and are occluded by the positive electrode active material, whereby stable repeated charging and discharging can be performed. . Here, the negative electrode active material is a composite oxide Li _x Si containing lithium after the first charge.
After O is generated, in the subsequent discharge-charge cycle, a lithium-containing silicon composite oxide Li _{x ′} SiO is formed except during complete discharge.

As is apparent from FIGS. 15 to 16, the battery K according to the present invention has a remarkably large charge / discharge capacity. Further, the decrease in discharge capacity (charge / discharge efficiency) with respect to the charge capacity is extremely small except for the first cycle, and the decrease in discharge capacity (cycle deterioration) due to repeated charging / discharging is also small. Furthermore, it can be seen that the difference in operating voltage between charging and discharging is extremely small over the entire charging / discharging region, the polarization (internal resistance) of the battery is extremely small, and large-current charging / discharging is easy.

The reason why the decrease (initial loss) in the discharge capacity in the first cycle relative to the charge capacity in the first cycle is slightly large is that the negative electrode active material is electrochemically charged with lithium ions during the charge in the first cycle. When it is occluded, it is mainly caused by a side reaction that occurs between graphite and a binder added to the negative electrode mixture as a conductive agent and a binder, and is also occluded in SiO of the negative electrode active material, so that it is discharged. L that remains without being released
This is probably because i exists.

(Example 10) This example is the same as Example 9 except that the negative electrode 23 and the positive electrode 25 produced in the following manner were used in place of the negative electrode 13 and the positive electrode 15 of Example 9. A similar battery L was produced.

The negative electrode 23 was manufactured as follows. Using the same negative electrode active material and negative electrode mixture as in Example 9, 2 ton / c
A negative electrode pellet was obtained by pressure molding into a pellet having a diameter of 15 mm and a thickness of 0.28 mm in m ² . This negative electrode pellet was adhered to the negative electrode case 11 with a negative electrode current collector 12 made of a conductive adhesive containing carbon as a conductive filler, dried under reduced pressure at 200 ° C. for 10 hours, and then dried on the negative electrode pellet to a predetermined thickness. The punched lithium foil of 14 mm in diameter was crimped. The lithium-negative electrode pellet laminated electrode thus obtained was used as a negative electrode.

The positive electrode 25 was manufactured as follows. Lithium hydroxide LiOH.H ₂ O, cobalt carbonate CoCO ₃ and boron oxide B ₂ O ₃ are mixed at a molar ratio of Li: Co: B of 1 :.
Weigh it to be 0.9: 0.1, mix well using a mortar, heat and calculate this mixture for 12 hours in the air at a temperature of 850 ° C., and after cooling, pulverize and size the particles to 53 μm or less. did. This firing and crushing and sizing were repeated twice to synthesize the positive electrode active material LiCo _0.9 B _0.1 O _{2 according} to the present invention.

This product was used as a positive electrode active material, graphite was mixed as a conductive agent, and fluorine resin or the like was mixed as a binder at a weight ratio of 80: 15: 5 to prepare a positive electrode mixture.
Next, this positive electrode mixture was treated at ² ton / cm ² and had a diameter of 16.2 m.
After pressure molding into pellets with a thickness of 0.52 mm, 10
What was dried under reduced pressure at 0 ° C. for 10 hours was used as a positive electrode.

The battery thus produced (hereinafter abbreviated as battery L) was left to stand at room temperature for 1 week and then aged.
The charge / discharge test described below was performed. By this aging, the lithium-negative electrode pellet laminated electrode of the negative electrode 23 spontaneously reacted by contacting the non-aqueous electrolyte in the battery, and substantially all the lithium foil was electrochemically occluded in the negative electrode mixture.

Regarding the battery L thus obtained,
As in Example 9, the constant voltage of 1 mA was applied to the end voltage of charging.
A charge / discharge cycle test was performed under the conditions of 4 V and a discharge end voltage of 2.0 V. The charge / discharge characteristics of the first cycle and the second cycle at this time are shown in FIG. 17, and the cycle characteristics are shown in FIG.

As is apparent from the figure, the battery L of this embodiment is
It can be seen that the battery K has remarkably excellent charge / discharge characteristics as compared with the battery K of Example 9. In particular, it can be seen that there is almost no decrease (initial loss) in the discharge capacity in the first cycle with respect to the charge capacity in the first cycle, which is significantly improved compared to the battery K of Example 9. This is due to a side reaction between lithium ions generated by charging and discharging and a conductive agent or a binder, or Si during charging.
By assembling a battery by preliminarily stacking an amount of lithium corresponding to lithium, etc., which is occluded in O and not released at the time of discharge, on the negative electrode mixture, and after the battery is assembled, the laminated electrode is exposed to the electrolytic solution in the battery. This is because the lithium spontaneously reacts with the negative electrode mixture and is occluded, so that lithium is not lost in the negative electrode during the subsequent charge and discharge.

Further, it is understood that the cycle deterioration is remarkably improved by using the composite oxide containing boron as the positive electrode active material. (Example 11) In this example, the following positive electrode active material and electrolytic solution were used instead of the positive electrode active material and electrolytic solution of Example 10. A similar battery was produced in the same manner as in Example 10 except for the positive electrode active material and the electrolytic solution.

The positive electrode active material of this example was prepared as follows.
did. Lithium hydroxide LiOH / H ₂ O and cobalt carbonate
CoCO₃ And silicon dioxide SiO₂ Li: Co: Si
Mortar, weighed so that the molar ratio of is 0.9: 0.1.
After mixing well, the mixture is heated to 850 ° C in air.
After heating and firing at the temperature of 12 hours and cooling, the particle size is 53 μm or less.
It was crushed and sized underneath. Repeat this baking and crushing twice.
Layered structure having an approximate composition of LiCo0.9Si0.1O2
A complex oxide of This as a positive electrode active material according to the present invention
I used it.

The electrolyte used was a solution of LiPF6 dissolved at 1 mol / l in a mixed solvent of EC and DEC at a volume ratio of 1: 1. The battery thus obtained (abbreviated as battery M) was also charged and discharged under the conditions of a constant current of 1 mA and a cutoff voltage of 4.4 V and a discharge end voltage of 2.0 V as in Examples 9 and 10. A cycle test was conducted. 1st cycle and 2 at this time
FIG. 19 shows the charge / discharge characteristics at the cycle, and FIG. 20 shows the cycle characteristics.

As is clear from the figure, the battery M of this embodiment is
It can be seen that the battery L has more excellent charge / discharge characteristics as compared with the battery L of Example 10. That is, by using the composite oxide containing silicon as the positive electrode active material, the same charge / discharge capacity as that of the battery L using the composite oxide containing boron can be obtained, and the electrolyte solvent is composed of EC and DEC. By using the mixed solvent, it is found that the cycle deterioration is remarkably improved as compared with the battery L using the electrolyte solvent containing PC and not containing DEC.

Example 12 Instead of the electrolytic solution of Example 11, LiPF was used in a mixed solvent of EC and DMC in a volume ratio of 1: 1.
_A solution of ₆ dissolved in 1 mol / l was used. A similar battery N was produced in the same manner as in Example 11 except for the electrolytic solution.

The thus obtained battery N of 1 kHz,
The internal resistance measured by the 1 mA AC method was 6Ω, which was half that of the battery M of Example 11, which was 11Ω. The battery N was also subjected to the same charge / discharge cycle test as in Example 11, and as a result, the charge / discharge capacity for each cycle was increased by about 20% as compared with the battery M, and the discharge capacity was decreased due to repeated charge / discharge. The (cycle deterioration) was almost the same level as the battery M. That is, EC and DMC are used as electrolyte solvents.
In the case of using the mixed solvent of, the charge / discharge characteristics superior to those in the case of using the mixed solvent of EC and DEC are obtained.

[0107]

As described in detail above, the present invention uses a novel active material composed of a lithium-containing silicon oxide or silicate as a negative electrode active material of a non-aqueous electrolyte secondary battery. The negative electrode active material has a remarkably large amount of lithium ions that can be reversibly occluded and discharged by charging and discharging in a base potential region of 0 to 1 V with respect to a lithium reference electrode (metal lithium), Since the charge / discharge polarization is small, it is possible to obtain a secondary battery having high voltage / high energy density and excellent charge / discharge characteristics at a large current. or,
Almost no deterioration such as generation of irreversible substances due to overcharging / overdischarging is observed, and a very stable secondary battery having a long cycle life can be obtained.

In particular, when a lower oxide Li _x SiO _{y of} silicon containing lithium (where x ≧ 0, 2>y> 0) is used, the charge / discharge capacity is particularly large and the charge / discharge polarization is high. It is small and easy to charge and discharge with large current, and it is especially excellent. In addition, by using _a composite oxide Li _a M _b L _c O ₂ having a layered structure containing silicon and / or boron as a positive electrode active material together with these negative electrode active materials, _a secondary battery is constructed, It is possible to obtain a secondary battery having a high operating voltage, a higher energy density, excellent charging / discharging characteristics, little deterioration due to overcharging / overdischarging, and a long cycle life.

Furthermore, by using a non-aqueous electrolyte containing ethylene carbonate as an electrolyte together with these negative electrode active materials, it is possible to obtain a secondary battery having a particularly long cycle life and high reliability, which has excellent effects. .

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of the structure of a battery used for comparative evaluation of negative electrode active materials in the present invention.

FIG. 2 is a negative electrode active material of a battery according to the present invention and a conventional battery.
It is explanatory drawing which showed the comparison of the charging characteristic of the cycle.

FIG. 3 is a negative electrode active material of a battery according to the present invention and a conventional battery.
It is explanatory drawing which showed the comparison of the discharge characteristic of the cycle.

FIG. 4 is a negative electrode active material of a battery according to the present invention and a conventional battery;
It is explanatory drawing which showed the comparison of the charging characteristic of the cycle.

FIG. 5 is a negative electrode active material of a battery according to the present invention and a conventional battery.
It is explanatory drawing which showed the comparison of the discharge characteristic of the cycle.

FIG. 6 is an explanatory diagram showing a comparison of cycle characteristics of a negative electrode active material of a battery according to the present invention and a conventional battery.

FIG. 7 is an explanatory diagram showing a comparison of charge characteristics in the first cycle of various negative electrode active materials of the battery according to the present invention.

FIG. 8 is an explanatory diagram showing a comparison of discharge characteristics in the first cycle of various negative electrode active materials of the battery according to the present invention.

FIG. 9 is an explanatory diagram showing charge / discharge characteristics at the third cycle of the negative electrode active material of the battery according to the present invention.

FIG. 10 is an explanatory diagram showing cycle characteristics of a negative electrode active material of a battery according to the present invention.

FIG. 11 is an explanatory diagram showing a comparison of charging characteristics of the negative electrode active material of the battery according to the present invention in various electrolytes at the fifth cycle.

FIG. 12 is an explanatory diagram showing a comparison of discharge characteristics of the negative electrode active material of the battery according to the present invention in various electrolytes at the fifth cycle.

FIG. 13 is an explanatory diagram showing a comparison of cycle characteristics of the negative electrode active material of the battery according to the present invention in various electrolytes.

FIG. 14 is an explanatory diagram showing an example of the structure of a battery implemented in the present invention.

FIG. 15 is an explanatory diagram showing charge / discharge characteristics in the first cycle and the second cycle of the battery according to the present invention.

FIG. 16 is an explanatory diagram showing cycle characteristics of the battery according to the present invention.

FIG. 17 is an explanatory diagram showing charge / discharge characteristics at the first cycle and the second cycle of the battery according to the present invention.

FIG. 18 is an explanatory diagram showing cycle characteristics of the battery according to the present invention.

FIG. 19 is an explanatory diagram showing charge / discharge characteristics at the first cycle and the second cycle of the battery according to the present invention.

FIG. 20 is an explanatory diagram showing cycle characteristics of the battery according to the present invention.

[Explanation of symbols]

 1 counter electrode case 2 counter electrode current collector 3 counter electrode 4, 14 separator 5 working electrode 6 working electrode current collector 7 working electrode case 8, 18 gasket 11 negative electrode case 12 negative electrode current collector 13 negative electrode 15 positive electrode 16 positive electrode current collector 17 positive electrode Case

 ─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 4-265179 (32) Priority date Hei 4 (1992) October 2 (33) Country of priority claim Japan (JP) (31) Priority Claim number Japanese patent application No. 4-202383 (32) Priority date Hei 4 (1992) July 29 (33) Priority claiming country Japan (JP) (72) Inventor Fumiharu Iwasaki 6-31 Kameido, Koto-ku, Tokyo No. 1 Seiko Electronics Co., Ltd. (72) Inventor Seiji Yahagi 6-31 Kameido, Koto-ku, Tokyo No. 1 Seiko Electronics Co., Ltd. (72) Inventor Akifumi Sakata 6-31 Kameido, Koto-ku, Tokyo No. 1 in Seiko Electronics Co., Ltd. (72) Inventor Tsugio Sakai 5-30-1 Nishitaga, Taihaku-ku, Sendai City, Miyagi Prefecture Seiko Electronic Components Co., Ltd.

Claims (9)

[Claims] 1. A non-aqueous electrolyte secondary battery comprising at least a negative electrode, a positive electrode and a lithium ion conductive non-aqueous electrolyte, wherein a lithium-containing silicon oxide or silicate is used as a negative electrode active material. A non-aqueous electrolyte secondary battery characterized by: 2. The composition formula Li _x SiO _y as the negative electrode active material.
(However, x ≧ 0, 2>y> 0) and a lithium-containing silicon oxide is used, and the non-aqueous electrolyte secondary battery according to claim 1. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the silicon oxide or the silicate containing lithium used as the negative electrode active material is amorphous. 4. The positive electrode active material has a composition formula of Li _a M _b.
L _c O2, where M is a transition metal element, L is one or more kinds of metal elements selected from boron B and silicon Si, and a, b, and c are 0 <a ≦ 1 respectively. .15,
0.85 ≦ b + c ≦ 1.3, 0 ≦ c, and a complex oxide having a layered structure is used.
The non-aqueous electrolyte secondary battery according to item 3. 5. The non-aqueous electrolyte comprises at least a non-aqueous solvent and a supporting electrolyte containing lithium ions,
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein a non-aqueous electrolyte solution containing ethylene carbonate is used. 6. The non-aqueous electrolyte is R · represented by the formula 1.
The non-aqueous electrolyte secondary battery according to claim 5, further comprising an R′-type alkyl carbonate. [Equation 1] 7. The non-aqueous electrolyte secondary battery according to claim 6, wherein the R · R′-type alkyl carbonate is dimethyl carbonate or diethyl carbonate. 8. By an electrochemical reaction between a silicon oxide or a silicate and lithium or a substance containing lithium in the battery after the battery is assembled or in the battery during the battery manufacturing process. 8. The non-aqueous electrolyte electrolyte according to claim 1, wherein the silicon oxide or the silicate absorbs lithium ions to obtain the silicon oxide or the silicate containing lithium. Next battery manufacturing method. 9. The silicon oxide is a lower oxide S of silicon.
9. The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 8, wherein iOy (where 0 <y <2).